This has a number of problems like it is not SVA friendly and if you happen to lose the wing nut, you are stuffed getting a replacement as it is 1/4 UNC - or something just as unobtainable.
So on Satruday I converted to use M6.
The hard bit is removing the bolt which is pressed in place.
The TIP is to use a narrow cold chisel to get between the nut head and the bracket; doing this from both sides releases the nut.
Then an M6 bolt is fitted - loctited into place and a nyloc fitted instead.
A rubber buffer can be placed onto the nut to take up the space between the brakcet and the cover plate since for some reason there is about 15 mm gap between the bracket and plate.